1. Field of the Invention
The present invention relates generally to apparatus and to methods for conditioning pads that are used in chemical-mechanical polishing or chemical-mechanical planarization processes, both of which are referred to herein as “CMP” processes. Particularly, the present invention relates to apparatus and methods for conditioning CMP pads with little or no contamination of the pads. More particularly, the present invention relates to apparatus for conditioning CMP pads, as well as to methods that include use of the conditioning apparatus and removing contaminants left on the CMP pad by the conditioning apparatus following conditioning of a CMP pad.
2. Background of Related Art
Chemical-mechanical polishing and chemical-mechanical planarization are abrasive techniques that typically include the use of a combination of chemical and mechanical agents to planarize, or otherwise remove material from or planarize a surface of a semiconductor material substrate bearing devices under fabrication. A chemical component, typically a slurry that includes one or more oxidizers, abrasives, complexing agents, and inhibitors, oxidizes the surface of one or more material layers that are being polished or planarized (i.e., at least partially removed). A polishing pad, or CMP pad, is used with the slurry and, along with abrasives present in the slurry, effects mechanical removal of the layer or layers from the surface of the semiconductor device structure. It should be noted that abrasive-only polishing and planarization, e.g., without the use of active chemical agents to effect material removal, are becoming more prevalent due to environmental concerns. Thus, the term “CMP” as used herein encompasses such abrasive-only methods and apparatus.
Conventional CMP pads are round, planar, and have larger dimensions than the semiconductor substrates (e.g., wafers or other substrates including silicon, gallium arsenide, indium phosphide, etc.) upon which the structures or layers to be polished have been formed. In polishing one or more layers of structures formed on a substrate, the substrate and the conventional CMP pad are rotated relative to one another, with the location of the substrate being moved continuously relative to the polishing surface of the pad so that different areas of the pad are used to polish one or more of the layers or structures formed on the substrate.
Another polishing format is the so-called “web” format, wherein the pad has an elongate, planar configuration. The web is moved laterally from a supply reel to a take-up reel so as to provide “fresh” areas thereof for polishing one or more layers or structures formed on a semiconductor substrate. A similar, newer, polishing format is the so-called “belt” format, wherein the pad is configured as a belt, or continuous loop, of polishing material. In both the “web” and “belt” formats, the semiconductor substrate is rotated upon being brought into contact with the pad. The pad is moved when a “fresh” polishing surface is needed or desired.
Conventional CMP pads are typically formed by forming the pad material into large cakes, which are subsequently skived, or sliced, to a desired thickness. Alternatively, CMP pads may be formed by injection molding processes. When injection molding processes are used to form CMP pads, a thicker, tougher skin may be formed on the exteriors of the pads, covering a pad material with the desired polishing characteristics. “Web” and “belt” format CMP pads may be formed by extrusion or other processes that have conventionally been used to form thick films.
In addition, following the formation of CMP pads, the surfaces thereof typically require conditioning to impart the CMP pads with sufficient surface roughness to trap slurry for effective polishing of a surface of a semiconductor substrate. Alternatively, as the exterior surface of a CMP pad may conceal interior portions thereof that have a structure that is desirable for use in polishing, a CMP pad may be conditioned to expose an interior region thereof. As another alternative, it may be desirable to alter features on the polishing surface of the pad prior to polishing one or more layers or structures on a semiconductor substrate with the pad.
A desired surface roughness of a CMP pad is usually imparted to the pad by a so-called “break-in” conditioning process following placement of the pad on a polishing tool. Conditioning is also used to remove slurry from a CMP pad polishing surface and to restore the desired surface texture or roughness and planarity to the polishing surface thereof after the pad has been used to polish semiconductor device structures. Typically, a pad is conditioned by dragging the same across a rough or abrasive pad conditioner, such as a diamond or diamond-on-metal conditioner. The pad conditioner may also remove surface irregularities (e.g., protrusions) from the CMP pad, improving the planarity of the pad. Conventionally, CMP pads have been conditioned by rotating one or both of the CMP pad and the pad conditioner relative to one another for time periods of twenty minutes or more. Conditioning is often effected using the same equipment that is used to rotate the CMP pad during polishing. As a result, conditioning may undesirably tie up the CMP equipment, as well as the equipment operator's attention, for long periods of time that could otherwise be used to polish semiconductor substrates. Moreover, conventional conditioning processes are sometimes ineffective.
A less effective conditioning method that may be employed includes the use of a particulate abrasive, typically silicon carbide or alumina, which is also referred to as corundum, to roughen the surface of a CMP pad. Abrasive fixtures, such as abrasive-coated papers, cloths, and rigid (e.g., steel, aluminum, or plastic) fixtures to roughen the surfaces of CMP pads are known. While these abrasive-coated conditioners inexpensively and reliably roughen and planarize CMP pads, the use of abrasive-coated conditioners is somewhat undesirable since the CMP pads may trap or become embedded with the abrasive particles. The particulate abrasive materials, such as alumina and silicon carbide, that are typically employed to roughen and planarize CMP pads are very inert and typically cannot be chemically removed from a CMP pad without damaging the pad. When one of these particulate abrasive conditioning materials is present on a CMP pad, the surface of a polished semiconductor device structure may be scratched or otherwise damaged by the abrasive conditioning materials. If an electrically conductive or organic layer that overlies an electrically insulative layer or structure is being partially removed or planarized by the CMP process, electrically conductive debris from the layer being planarized or otherwise removed may be trapped in the scratches, or otherwise damaged areas of the surface of the semiconductor device structure. Such trapped debris may subsequently cause electrical shorting of a fabricated semiconductor device. For example, if CMP processes are used to remove mask material and at least part of a conductively doped HSG silicon layer from an insulator at the surface of a stacked capacitor structure, conductive silicon particles may be trapped in voids or vugs comprising defects in the surface of the insulator and subsequently cause electrical shorting between adjacent containers of the stacked capacitor. These potentially damaging contaminants may remain even when a chemical material removal process, such as a wet or dry etch, follows the CMP process.
The art lacks teaching of a conditioning apparatus and method that may be used to efficiently condition a CMP pad without consuming valuable CMP process time and with which unwanted particulate abrasive contaminants may be substantially removed from the CMP pad.